Automotive suspension materials type query 2

[johnd100]

Hi,

I've posted this in the automotive section but I think it's more of a materials query so have posted here too.

My suspension uses two link shafts to transfer the movement from the control arm to the shock absorber via a cam link.I am looking to manufacture some of these link shafts and was debating the best material to use. I assume the main loads are going to be bending loads and to this end I was thinking something along the lines of rolled 4130 bar. I'm pretty sure the OEM manufacturer won't tell me what they use so would be interested in anyone's feedback.

I've attached a basic diagram of the arrangement. Two round shafts that taper to locate with a threaded end to lock in place.

Many thanksJohn

 

[swall]

You need to first determine your stress levels.

 

[johnd100]

I actually have the shaft I want to replace. Is there any way to check what material type it is through analysis? The one I was designing to replace it was going to be of a larger diameter anyway.

Thanks

John

 

[DVWE]

Probably the best way to check material type is to have a metallurgical lab perform a chemical analysis with optical emission spectrometry. The lab will probably be able to tell you what the material is based off of that. That might be the best way to figure out what the material is unless you can talk to someone that can tell you for sure - like the design engineer who designed it.

 

[TVP]

John,

Chemical composition and a hardness check will essentially tell you the material and heat treatment. An independent met lab will charge about $200 to perform these two tests on one piece.

 

[johnd100]

The reasoning behind this is I am trying to take some non-servicable parts and make them servicable.

To this end I may now actually retain the exisiting shafts, of a known strength, and work on making the housings servicable.

It may be the easiest course of action as opposed to a complete re-design.

John

 

[tbuelna]

johnd100,

Besides the material composition and hardness checks recommended above, you should also carefully evaluate the metal's grain structure, any indication of surface working (such as fillet rolling or shot peening), as well as the type of fit (such as press fits) between any mating parts.

Most people don't appreciate just how highly engineered production automotive parts really are. The OEM's spend lots of time figuring out how to get the most performance from the lowest cost materials. They know lots of tricks to maximize fatigue life, and some of what they do to the part/material may not be readily apparent.

Good luck.
Terry

 

[TemperedMartensite]

Good point Terry.

 

[Tmoose]

Could you post some photos, too?
When I looked at the jpg I thought the "shafts" are subjected to bending

 

[johnd100]

Hi All,

Many thanks for all the info.

I have now decided I am going to try to replace the bearing materials that the shafts run on as opposed to replacing the shafts themselves as it may be a wholly easier proposition.

If I do decide to replace them ill certainly send them off for analysis and mechanical testing.

Regards

John